Emma Bunting, a poverty-stricken landlady in Victorian London, takes in a gentlemanly lodger who gives financial help to her and her husband George. Slowly it emerges that the lodger is not what he seems, and his religious mania indicates mental and other problems. As the tension mounts and the atmosphere becomes more sinister, Emma agonises over whether to report him to the authorities. The lodger's identity is revealed as Jack the Ripper.